Remove depends_on from Core Configuration option

[GustavoCaso]

What does this PR do?

Based on internal conversations, we agreed that depends_on is a feature from the past and that is no longer used. It has been replaced with the different components. Because of that we agreed that it was good to remove it 🔥

Motivation:

We are cleaning up the codebase from options we no longer use.

I was able to remove the following:

• The depends_on option from the configuration DSL
• Configuration::DependencyResolver.
• Configuration::OptionDefinitionSet. It was inherited from Hash, and the only functionality added was to organize the options in order using the depends_on attribute. I replaced it with a normal Hash.
• Configuration::OptionSet. It was inherited from Hash, but we were not extending the class with any particular functionality. I replaced it with a normal Hash.

Additional Notes:

How to test the change?

CI must be 🟢

For Datadog employees:

• If this PR touches code that signs or publishes builds or packages, or handles
  credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.

Unsure? Have a question? Request a review!

[marcotc]

Let's make sure to include in this in our changelog.

Because this feature hasn't been functional to its advertised intent for quite some time, I'm 👍 to remove it in its current form.

[ivoanjo]

Nice, hooray for less complexity! :)